This protocol will examine several animal models of alcoholism in rats: isolation-rearing, the Fawn hooded strain and the effects of 5,7-DHT lesions of the serotonin systems. This project continues previous work which was supported by a National Research Council Research Associateship (FSH). In these models, behavioral and neurochemical examinations of subjects will be made as well as examination of responses to ethanol. In particular, differences in the effects of serotonin and dopamine responses to ethanol will be examined using in vivo microdialysis to measure the brain levels of these neurotransmitters. In addition, the alpha-methyl-tryptophan method will be evaluated as a technique for examining central serotonin function.